When transferring signals between two electronic devices, it is preferable to minimize a number of contacts between the devices. For example, reducing a number of pins on charging/data cables for mobile devices, as well as a number of contacts in the mobile devices, helps to provide more room for other technology in the mobile device. This is particularly true for small form factor devices, such as smartwatches, earbuds, Bluetooth headsets, head-mounted displays, etc. Moreover, an increased number of contacts increases a possibility of error and reduces reliability. For example, an increased number of contacts results in an increased probability that one of the contacts will become damaged or worn out or otherwise defective. However, because various types of signals typically need to be transmitted, such as power signals, data signals, control signals, etc., reducing the number of contacts can be quite challenging. Further challenges are presented by reducing a size of the contacts.
In some systems, data can be transmitted over existing AC electrical distribution wiring between transformers, and electrical wiring between transformer and customer outlets. In these systems, a modulated carrier signal is added to the wiring system. However, power wire circuits require insertion of a bulky inductive impedance, complex modulation, and complex demodulations. They have limited applications.